Turns out my problem was an o-ring failure on ones the shop had replaced. They figured they got a bad lot and did it under warranty. Keeping my fingers crossed from now on.
However, since I got it back I've had noise coming from under the glove box when I step on the gas. It sound like a fan whirring, or possibly the normal engine noise with some sound proofing missing. It gets louder the harder I accelerate, and doesn't seem to depend on rpm or speed. Any ideas?